Stable isotope analyses as a forensic tool to monitor illegally traded African grey parrots

Stable isotope analyses are a powerful tool in understanding diets, defining trophic networks, inferring geographical origins of animals and in forensic tracing of the origins of deceased humans or illegally traded animal and plant material. African grey parrots Psittacus erithacus are one of the most traded animal species in the world, and the origin of confiscated illegal or deceased specimens are often unknown. We measured stable isotope values (δ¹³C, δ¹⁵N and δ²H) in different African grey parrots (n = 32) and determined feather type (i.e. primary, tail, breast) standardization values for comparing individuals. δ¹³C and δ²H values differed between known wild (n = 42) and captive (n = 50) birds when standardized for feather type, but not for δ¹⁵N. δ¹³C and δ²H values in feathers from a consignment of African grey parrots (n = 100), all of which were deceased, aligned significantly with that of known wild birds. We suggest that further analyses of feathers, across a range of spatial and temporal scales, will enhance stable isotope analyses as a valuable tool in monitoring and combatting the trade of African grey parrots. Furthermore, the use of stable isotope analyses may improve the monitoring of illegally traded bird species, and other wildlife, across the globe.